IT KNOWLEDGECA Professional Stage - Knowledge Level, ICABTutor: Mohammad Abdul Matin

Chapter 4Communication and IT

Chapter Outline

Communication System

Computer Network

Network Software

Network Topology

Communication Protocol

Communication System

Communication is a process of transferring messages from one point to another. The basic elements of a communication system are:

– A sender

– A medium

– A receiver

Data Transmission Modes

Simplex

– Only in one direction

Half-duplex

– Both direction, but not simultaneous

Full-duplex

– Simultaneous both directions

Information Delivery Types

Unicast: e.g. HTTP, SMTP, POP3 Broadcast: e.g. DHCP

Multicast: e.g. Video transmission to specific devices

Computer Network

Classifications of Network

– Local Area Network (LAN)• Within close proximity

• Resources can be shared

– Metropolitan Area Network (MAN)• Larger than LANs and may connect multiple LANs in a specific area

• Generally not owned by any single owner

• Sometimes can be used to share regional resources

– Wide Area Network (WAN)• Covers very large geographical areas

• Generally not owned by someone

• Sometimes can be point to point (e.g. telephone network)

Network Devices

Router

– Connects between / among two or multiple different networks (LAN-LAN, LAN-WAN or WAN-WAN)

– Determines data packets’ destinations based on information stored in routing tables

– Can find best path (least cost) based on the paths’ priority settings configurations in the router

– Networks are generally separated by different IP address blocks

Network Devices

Switch

– Connects multiple computers/devices within a LAN

– Can analyze the data packets and determine/control packet flow to the right device(s) reducing network load

– Can be of different speed capacities like 10 /100 / 1000 mbps

Bridge

– Connects one LAN to another LAN based on same protocol

– Filters/controls traffic based by identifying destinations

– Generally uses a single port for uplink/downlink

Network Topology

Linear Bus Topology

Ring Topology

Start Topology (mostly used in LANs)

Tree (expanded star) Topology

Hierarchical Topology

Mesh Topology (used for devices like fire detection)

Roles of Protocol

Data Sequencing (breaks messages to packages and to data frames)

Data Routing (dynamically determines most efficient paths)

Flow Control (balances speed between sender and receiver)

Error Control (discards at receiver’s end when block has error)

Precedence and Order Transmission (prioritize and control to

give all devices a chance)

Connection Establishment (handshaking, verification)

Data Security (by splitting in various segments, it prevents from

unauthorized access to data)

Log Information

OSI Model

Open System Interconnection (OSI) model is a reference model developed by ISO in 1984.

It is a conceptual framework for setting standards for communication within a network among different devices.

Adopted by all vendors (manufacturers) of devices as a standard.

OSI model defines the communication process in seven layers.

OSI Model – The 7 Layers

1. Applicationsupports application services for users’ usage. e.g. Email, file transfer, etc.

2. Presentationworks as an adapter to transform data from application format to network format and vice versa. Formats, encrypts or decrypts data.

3. SessionEstablishes, manager and terminates connections between applications.

4. TransportResponsible for point to point error control / recovery and data flow control.

OSI Model – The 7 Layers

5. NetworkCreates network paths and enables routing, switching and forwarding.

6. Data LinkPackets are encoded and decoded into bits.

7. PhysicalConveys the bit stream as electrical, light or radio signals through the electrical and mechanical levels.

OSI Model – The 7 Layers

OSI Model – The 7 Layers

Exam Questions

Write down differences between LAN, MAN and WAN.

What are the different types of Network Topology? Describe any one of them.

Write down difference between unicast, broadcast and multicast.

Describe the seven layers of OSI model.

Thank You